1. Field of the Invention
The present invention relates to electronic inverters, particularly to self-oscillating full bridge inverters using bipolar transistors.
2. Description of Prior Art
When a self-oscillating full bridge bipolar-type transistor inverter is loaded with an inductive load, after then end of each half-cycle of the inverter's high-frequency output voltage, current will continue to flow in the bridge for at least a short period after the two most recently conducting transistors have ceased conducting, yet before the obverse two transistors have started to conduct.
As a result of this lingering inductive current, the inverter's bipolar transistors will tend to switch off rapidly and therefore give rise to high-efficiency inverter operation.
However, when a self-oscillating bipolar-type full bridge inverter is used with a purely resistive load, no lingering inductive current results and low-efficiency inverter operation is apt to occur.
U.S. Pat. No. 4,502,107 to Nilssen describes a full bridge self-oscillating bipolar-type transistor inverter wherein the net inverter load is made inductive by the overt addition of an inductor in parallel with the inverter's otherwise resistive load. However, in order for this method to work well, there has to be a matching between the value of the inductor and the load; which requirement may represent a drawback in some applications.